I don't see an "official" French Vista DVD on the M$ MSDN wesite. Why don't you install Vista Ultimate and download the French language pack via Windows Update?
Just to update (unrelated to french version): the link in the second post should work too; I never got it to work, but it's probably just me, still, even then I got very close twice before the downloads finished prematurely
the ftp link needs passwords now, is there some other link (like rapidshare) that works for msdn 32bit vista (my laptop can't use 64bit)?